Michael Ballack has given Chelsea the first potential headache resulting from Fifa's decision to ban the club from operating during the next two transfer windows by warning that he may retire following the 2010 World Cup in South Africa.

The sanctions imposed by football's governing body for what it says was the illegal acquirement from Lens of Gaël Kakuta, an 18-year-old French forward, means Chelsea, unless they win an appeal before the Court of Arbitration, have to rely on their 24-man first-team squad plus reserves for success until January 2011.

Ballack, 32, is thought to earn around £120,000 a-week on the four-year deal he signed in 2006. And while the Germany captain has started the season impressively, scoring twice in the Premier League, he says serious consideration will be given to his future next summer. "I will decide after the 2010 World Cup if I will continue playing or if I will stop," he said. "I will continue as long as I enjoy it and still have ambitions in the sport."

Chelsea might have been expected to open negotiations with the midfielder, who is in Germany ahead of a friendly with South Africa, around 18 months before the end of his contract but had so far refused, suggesting he might be allowed to leave next June. But Fifa's judgment, plus Ballack's own announcement, may force their hand into immediate contract talks.

Salomon Kalou, Ballack's Chelsea team-mate, also has only a year remaining on his deal but there may be better news for the club after Jan de Visser, the Ivory Coast forward's agent, told the Guardian he plans to meet the Stamford Bridge hierarchy over the next fortnight. "I will meet Chelsea sometime around the game with Porto," De Visser said of the opening Champions League group match on 15 September. "Salomon is in the Ivory Coast now with the national team and Chelsea want to speak about the new contract."

Asked if Kalou is open to a fresh deal, he replied: "Yeah, he's definitely interested in speaking with Chelsea, of course."

De Visser also confirmed that Kalou's contract talks were planned before Thursday's revelations about Kakuta. "We have been speaking for months with Chelsea."

As with Ballack, Joe Cole, Deco, Juliano Belletti and Alex, whose contracts are all due to finish by January 2011, Kalou's bargaining position can only have been strengthened by their potential inability to buy any new players.

But De Visser denied that the 24-year-old would seek any financial advantage from the club's predicament. "Maybe he was already in this position because his contract was finishing," he said of Kalou. "And, I know the situation with Chelsea at the moment but let's see as maybe they will appeal and [win]."

Frank Arnesen, meanwhile, Chelsea's director of football who was instrumental in completing the Kakuta deal, is not thought to be under threat. Any dismissal of Arnesen before the CAS appeal might be viewed as an admission of guilt by Chelsea. The Dane is supported strongly by Roman Abramovich, but his position at the club may be reviewed once the fall-out from the Kakuta saga has cleared.